In the plastics industry, many product applications require flame retardant plastic compositions. In some cases, this can be achieved by using inherently flame-retardant plastics, such as halogenated polymers. In other cases, plastics that are not inherently flame-retardant are required, and flame retardant additives must be added to the plastics composition. However, many of the most effective flame retardant additives are halogenated compounds that are currently disfavored for health or environmental reasons. Furthermore, when non-halogenated flame retardant additives are used, they often must be employed in high concentrations to achieve the desired flame retardancy, and these high concentrations detract from the desired physical properties of the plastic composition. There is therefore a need for flame-retardant compositions that are both halogen-free and effective at low concentrations.